DNA vaccines offer an attractive alternative to create effective vaccines that are inexpensive to manufacture, and can be widely distributed. One of the most difficult tasks in developing a DNA vaccine is the identification of the antigen that will stimulate the most effective immune response against the pathogen, particularly when the genome of the infectious organism is large. A technology developed by Gene Therapy Systems Inc. under a previously funded SBIR grant (R43 AI47641-01) will be applied to the general problem of how to identify potent DNA vaccine antigens from complex organisms. The technology called Transciptionally Active PCR (commercial name "TAP ExpressTM") is a method for generating functional PCR fragments that can be used directly in in vitro transfection assays and in vivo. TAP fragments are as active as supercoiled plasmids in all assays examined including DNA vaccine immunizations, enabling high throughput functional screening of a very large number of genes, on a scale that has not been previously possible. In this proposal several enhancements will be added to the technology and it will be used to screen 424 malaria antigens with the goal of identifying new DNA vaccine antigens that have improved protective immunological activity. PROPOSED COMMERCIAL APPLICATION: The resources from this grant will be used to continue the development of a practical method for generating transcriptionally active PCR (TAP) fragments, which can be used directly in in vitro transfection assays and in vivo. A high throughput vaccine antigen screening system will be developed to enable the identification of potent vaccine antigens from complex organisms such as malaria.